Release coated adhesive tape

ABSTRACT

Release coated pressure sensitive adhesive tape utilizing release coating compositions that are alkyl sulfide, alkyl sulfoxide and alkyl sulfone terminated oligomers. Superior release, printability, water base non-polluting characteristics and high temperature-high humidity aging resistance are obtained.

United States Patent [191 Settineri et al.

[ RELEASE COATED ADHESIVE TAPE [75] inventors: Robert A. Settineri,Telford, Pa;

John T. O'Brien, Cheshire, Conn.

[73] Assignee: W. R. Grace & Co., Cambridge,

Mass.

22 Filed: Dec.30, 1974 2: Appl. No.:537,625

[56] References Cited UNITED STATES PATENTS 3,498.943 3/1970 Dannals260/855 Dec. 23, 1975 Dannals 260/4654 Peaker 260/79] PrimaryExaminer-George F, Lesmes Assistant Examiner-R. J. Roche Attorney,Agent, or FirmEdward J. Hanson, Jr.; C. E. Parker 57 ABSTRACT Releasecoated pressure sensitive adhesive tape utilizing release coatingcompositions that are alkyl sulfide, alkyl sulfoxide and alkyl sulfoneterminated oligomers. Superior release, printability, water basenon-polluting characteristics and high temperature-high humidity agingresistance are obtained.

29 Claims, No Drawings RELEASE COATED ADHESIVE TAPE BACKGROUND OF THEINVENTION The disclosure of the composition of the oligomers iscontained in US. Pat. No. 3,668,230, June 6, 1972 (Dannals) and US Pat.No. 3,839,405, Oct. 1, i974 (Dannals). These patents disclose thegeneral class of alkyl thio, sulfoxide, and sulfone terminated lowmolecular weight polymers.

The use of the oligomers as emulsifiers is further disclosed in US Pat.No. 3,498,942, Mar. 3, 1970 (Dannals) which discloses the use of alkylthio-terminated oligomers, having appendent cyano and carboxyl groups onthe oligomeric portion as emulsifiers in emulsion polymerization, in US.Pat. No. 3,632,466, Jan. 4, i972 (Peaker) which discloses stabilizinglatex coating compositions containing the oligomers and in U.S. Pat. No.3,772,382, Nov. 13, i973 (Dannals), US. Pat. No. 3,776,874, Dec. 4, i973(Dannals), and US. Pat. No. 3,759,860, Sept. 18, 1973 (Peaker), whichdisclose similar use for the alkyl sulfoxide and sulfone-terminatedoligomers.

No use of the oligomers as release agents has been disclosed.

Many present day non-printable release coatings are made up in organicsolvents such as toluene, benzene or aqueous organic solvents such as analcohol water solvent. These organic solvents, due to their pollutingeffect, supply problems and rising cost are beind abandoned. Such arelease agent is polyvinyl n-octadecyl carbamate as set forth in US.Pat. No. 2,532,0ll (Dahlquist et al.).

Many present day printable release coatings are also in use which arenon-polluting but virtually all such coatings fail badly when aged underhigh humidity conditions. Such release coats are available as anioniclatices of acrylonitrile ethyl acrylate copolymers containing 27 weightpercent acrylonitrile. The present invention combines the desirableproperties of both types inone and the same material.

SUMMARY OF THE INVENTION mula:

1 $1 R-S(Olwherein R is an alkyl group having from 12 to 22 carbonatoms; R and R may be the same or different and are hydrogen, a CH or aC.,l'l group; R is hydrogen, a CH;,, -C H, or COOR group, and R ishydrogen, a -CH C H COOR or CH- COOR group, provided that R is otherthan COOR-" if R is COOR" or -CH,COOR"; R is hydrogen or a cation basedon an alkali metal, ammonia or an amine; (a-l-b) is from 4 to I00,a/(a+b) is from 0.0 to 0.6; and n has a value OH), I or 2.

The release coating may be applied to conventional surfaces usuallycontacted with pressure sensitive adhesive materials. Such surfacesinclude but are not limited 2 to paper, rubber latex impregnated paper,non-fibrous regenerated cellulose film, fiberglass, plastic and thelike.

One object of the instant invention is to provide a pressure sensitivetape structure having a release coating which when engaged with theadhesive reduces the amount of pull required to peel the adhesive fromthe backing material without appreciably decreasing the adhesiveness ofthe adhesive material which has been removed. Another object of theinstant invention is to provide such a tape structure having the releasecoating deposited from water thereby eliminating problems such aspollution caused by organic solvents and the like. Still another objectof the invention is to provide a release coating that is odorless andnon-toxic. Other important objects are to provide a tape structurehaving the adhesive engaged with a release coating in which the releasecoating is printable and resistant to deterioration, particularly whenthe assembled tape structure is subjected to high temperature and highhumidity. Another object is to provide a tape structure having lowunwind forces at high unwind speedand resistance to unwind forcebuild-up after aging at high temperature and high humidity. These andother objects are obtained by the release coating and tape as sembly ofthis invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT The present invention, in apreferred embodiment, is a self-wound pressure-sensitive adhesive tapecontaining a flexible backing. One side of the backing is coated with apressure-sensitive adhesive and the opposite side is coated with arelease coating. When the tape is wound on a roll the adhesive isengaged against the release coating. When the tape is unwound theadhesive is disengaged from the release coating. A most importantproperty is, of course, the quality ifthe adhesive of the tape after itis removed from contact with the release coating. in addition it isimportant that the engagement of the adhesive with the release coatingbe such that the roll structure is maintained integral until it is timeto use the tape and that the adhesive surface be protected from externalcontamination.

in the present invention the entirely new component of the tape is therelease coating. The essential composition of this release coating isthe oligomer described in the SUMMARY OF THE INVENTION section above.

The average molecule of the oligomer may be represented by the formulaas described above. The formula is not intended to depict the actualstructure of the oligomers because the structural units are randomlydistributed throughout the molecule. In the formula R is linear orbranched primary, secondary or tertiary alkyl radical having from 12 to22 carbon atoms such as 2-dodecyl, 3-dodecyl, 2,3-dimethyldecyl,2-ethyldecyl, 2,5'dimethyldecyl, n-pentadecyl, 2-hexadecyl,n-heptadecyl, Z-heptadecyl, 2-methyl-2-hexadecyl, 2-octadecyl,Z-methyl-Z-heptadecyl, 2-ethyl-2hexadecyl, nnonadecyl, n-eicosyl,seceicosyl, n-heneicosyl, ndocosyl and others. Preferably R is a linearor branched primary alkyl or a linear secondary alkyl radical havingfrom 13 to 20 carbons, most preferably R is a linear or branched primaryalkyl group having from 13 to [8 carbons atoms; R and R are hydrogen, ACH or C H, group, R is hydrogen, a CH,,, C,H,, or -COOR" group, and R ishydrogen, a CH;,, C H,,,

COOR or CH COOR group, provided that R is other than -COOR if R is COORor CH- COOR; R. R R and R are preferably hydrogen. R is hydrogen or acation based on an alkali metal such as lithium, sodium, or preferablypotassium, or based on ammonia or a primary secondary or tertiary aminesuch as mono-, diand triethylamine, dimethylethanola mine,diethanolamine, triethanolamine, also morpholine, piperidine, pyridineand others.

The subscripts a and 1) indicate the total moles of monomers containingthe CN group and the total moles of monomers containing the COOR grouprespectively per molecule. The degree of polymerization may be expressedas the sum of a plus b, the value of (a+b) ranging from 4 to 100,preferably from S to 50 and most preferably from 12 to 50. The molefraction of the CN group carrying monomers within the molecule isrepresented by the expression a/(a-l-b) which usually has a value offrom 0.0 to 0.6, preferably from 0.0 to 0.5 and most preferably from0.25 to 0.5. The subscript n has a value of 0, l or 2, most preferably0.

The preferred oligomers of this invention are produced by thecopolymerization of acrylic acid with acrylonitrile in alcohol, forexample, methanol, ethanol, or isopropanol, and in the presence of amercaptan, for example, n-octadecyl mercaptan, such that amounts of eachmonomer species correspond to the desired levels of a and b in theproduct. The oligomers so prepared may then be neutralized with a basesuch as potassium hydroxide.

The oligomers are usually stripped of unreacted monomer and alcohol, forinstance by sparging steam through the solutions. The stripping may beperformed with the acidic reaction product or the partially orcompletely neutralized product. The point at which such stripping isperformed is not critical to the utility of the product as a releaseagent. Furthermore, the stripping itself is not essential to the utilityof the oligomers. The unstripped solution of the neutralized product maybe used as a release agent for pressure sensitive adhesives withoutfurther purification or removal of traces of catalyst, monomer residues,or solvent. The reaction solids during polymerization are also notcritical as far as the utility of the oligomers is concerned.

A portion of the neutralized product in the aqueous or aqueous alcoholsolution may tend to cream; but upon agitation readily reverts to itsoriginal uniform state. The neutralized product usually is furtherdiluted with water to low solids such as a 2 to 3 per cent oligomerconcentration in order to afford a solution more suitable for coatingpaper to form a release coated paper. Further details of the preparationof the oligomers useful in this invention are in U.S. Pat. Nos.3,498,942 and 3,668,230 incorporated by reference herein.

The essential composition of the release coating may be applied tosubstrates in various ways. The coating may be applied directly to oneside of a tape already coated or to be coated on the other side with apressure sensitive adhesive. The coating may also be applied to one orboth sides of a removable liner that is to be engaged by an adhesivesuch as a pressure sensitive adhesive. The coating may be applied in theform of a solution or a dispersion by conventional means well known inthe art, e.g. the solution or dispersion may be pumped, poured orsiphoned without deleterious effeet, and may be applied to the tapesubstrate by spray- 4 ing, doctor blading, roller coating, dipping,brushing. air-knifing or Mayer rod coating.

After application of the release coating to the sur face, the materialis dried by conventional means, i.e. heating the material attemperatures in the range 230 (C) to 380F (C) in conventional dryingovens or other well known means. This heating step not only facilitatesevaporation of the water and any solvent present in the release coatingcomposition but also causes the material to flow enhancing uniformity ofthe coating. However, it should be noted that after applying theoligomer, heating is not a necessary step to obtain a film havingrelease properties. The coated surface can even be allowed to dry atroom temperature.

In applying the release coating composition to the substrate, the amountof total solids in the dispersion or solution should be sufficient toprovide a very thin film on the substrate, said film being effective asa release coating. Conventional release coatings usually havethicknesses of a fraction of 21 mil. Coated weights in the range 0.001to 0.1 ounce/square yard (0.034 to 3.4 g/m exclusive of additives aresufficient to obtain a substantially continuous thin film of the releasematerial on the substrate surface.

The release composition of the instant invention may contain othermaterials well known in the art of release coating compositions inconventional amounts which do not materially affect the releasecharacter of the composition. For example, the composition may containpigments such as titanium dioxide or phthalocyanine blue. Additionallythe composition may contain extenders such as mineral fillers, inertresins or thermosetting resins as the use may require.

A preferred form of the invention would have the following parameter. Anadhesive engaged with an release coating, the release coating beingcomprised of an oligomer represented by the form 1 wherein R, R, R, R, Rand R as well as the subscripts a; b and n have the meanings set forthabove.

The oligomer preferably has a molecular weight between 200 and 5,000 andis applied from a aqueous solution or dispersion. The release coatingoligomer is preferably present in a quantity of 0.01 to 0.04 oz/yd (0.34to 1.4 g/m).

The preferred embodiment would be in the form of a pressure sensitiveadhesive tape with a flexible backing of creped cellulose sheetsaturated with latex, exemplary latices are ABS, acrylic, SBR,acrylonitrile, neoprene and copolymers and blends thereof. The sheet isusually in the form of a long tape. A base coating is preferably appliedto the backing surfaces that are to R-SiO);

be coated with the release coating. The base coating is.

preferably a vinyl or an acrylic latex, exemplary vinyl latices would befilms deposited from poly(vinyl acetate), poly (vinyl chloride), poly(vinyl chloride-acrylic) or blends of these with other coating laticesfamiliar to those skilled in the art. Preferably the release coatingwould be on one side of the flexible backing and the adhesive on theopposite side, and the tape is wound upon itself. The side of such apressure sensitive tape coated with the release coating may be calledthe back side while the side with the adhesive may be called the frontof the tape.

The invention is further illustrated by the following examples:

EXAMPLES General procedure for preparing the alkyl sulfide terminatedoligomers.

The oligomeric material having the general formulaalkyl-S-(acrylonitrile), (acrylic acid) H is prepared in methanol usingammonium persulfate as the initiator or in isopropanol using decanoyl orlauroyl peroxides as the initiator. Activators such as N,N-dimethylaniline (DMA) may be added as required.

The acrylic acid, acrylonitrile, alkyl mercaptan, and solvent(isopropanol) are added to a reaction vessel which is set in a waterbath or jacket preset to the reaction temperature and equipped with anaddition funnel, a thermometer or thermocouple, an agitator, a watercooled condenser, and a nitrogen inlet. Nitrogen gas purges the air(which contains oxygen) from the reaction vessel providing an inertatmosphere. Agitation of the solution is begun and nitrogen flow isstarted immediately thereafter. When the reaction temperatureequilibrates to the bath temperature, the initiator in solution in thesolvent (isopropanol) is added at a controlled rate of about l g ofinitator per mole of monomers per minute. The initiator solutionconcentration may be one gram oflauroyl peroxide per ml of isopropanol.If so desired the initiator may be added neat. About 0.25 ml of DMA permole of monomers may be added to the reactor if required. Since thereaction is exothermic. constant reaction temperature is maintained bycooling.

EXAMPLE I The following materials are combined in a l quart bottleaccording to the procedure outlined above in order to produce thefollowing oligomers:

n-octadecyl-S-(acrylonitrile (acrylic acid) H ml acrylonitrile (16g,0.302 moles) 60 ml acrylic acid (63g, 0.877 moles) 84 mln-octadecylmercaptan in isopropanol (25g/l00 ml) 59 ml isopropanol l0 ml10% decanoyl (l0g/l00 ml) In addition 1 ml of 25% DMA in isopropanol(25g/l00 ml) can be added, if desired, to increase the reaction rate,but it is not essential as far as the final composition and utility ofthe oligomer is concerned.

(As set forth in subsequent Example this oligomer would be Rn-octadecyl; a-t-b 16.0; a/(a+b) 0.256; acrylonitrile g= l6; acrylicacidg= 63; mercaptan 3 2]; catalyst g/mole 0.85.)

The bottle is sealed after all reagents have been added and is immersedin a water bath set at 50C. After l6 hours the sample is removed, andhas 40% solids. The acidic reaction product is a clear. straw coloredsolution at 50C, but becomes a viscous, two phase slurry upon cooling toroom temperature 22C).

Neutralization is carried out as follow: 50 ml water are added to [50gacidic reaction product. Neutralization is performed using oneequivalent of KOH (about 75g of 45% KOH). After 20% of the KOH has beenadded, the mixture is stripped of the unreacted monoperoxide inisopropanol mers and solvent by placing the mixture in a Buechi ModelVE-50 Rotovapor under vacuum. After stripping, the remainder of the KOHis added until a pH of 9 is obtained.

In order to evaluate the release agent the solution is diluted withwater to a total solids of about 2.5% and coated onto commerciallyavailable 8%: X l 1 inch tape backing sheets, i.e. ENDURA (trademark)13497. W. R. Grace & Co. A number 20 Mayer rod is used for obtaining adry coating of about 0.03 oz/yd. (1.12 g/m after drying at 375F (190C)for l minute. The release coated test backing so obtained is laid on aflat surface and 1 inch (2.54 cm) wide commercially available adhesivetape, i.e., Armak PF-Z, Armak Tape Company, is applied to the testbacking so that the machine direction of the adhesive tape parallels themachine direction of the test backing. Using at 4V: pound (2.04 kg.)roller the test tape is rolled against the test backing 3 times in eachdirection. Samples of the laminate are cut to convenient sizes, slightlywider than the l inch adhesive tape, and aged by I. being subjected tostandard conditions, i.e. 23 i 2C and a relative humidity of 50 i 2% atthat temperature for 76 hours; or

II. being subjected to accelerated aging conditions of high temperatureand high humidity by being placed in a desiccator containing saturated(NHU SO solution and held at [50F 2F (66 i 2C) for 72 hours. Therelative humidity is approximately Thereafter the samples are subjectedto the standard temperature and humidity conditions of (l) for 4 hoursbefore testing.

The aged samples are then evaluated using several tests: An average of 3test at each aging condition is performed.

Test A Aged samples are subjected to a hand zip test by placing them ona flat horizontal surface. While one hand is holding the backing down tothe surface, the other hand pulls the test tape rapidly (approximately200 ft./min) (6lm/min) from the backing at an angle of l80. The samplefrom both aging conditions removed readily without any noted tearing,adhesive transfer, delamination or any other damage to the adhesivetape.

The performance of the samples is rated according to the followingnomenclature:

l very easy to pull, superior performance 2 easy to pull 3 pull requiresmedium effort 4 somewhat difficult to pull 5 difficult to pull, stiffFor the sample aged under condition (I) the rating is l, and for thesamples aged under condition (ll) the rating is 2 on the average.

Test B Other aged samples are tested in accord with PSTC-l (PressureSensitive Tape Council Test Methods, 5th Edition) in an adhesion tobacking test.

The aged samples are attached to a steel test panel using double facedpressure sensitive tape. The free end of the test tape is doubled backat an angle of and peeled from the backing for a distance of 1 inch(2.54 cm). The tape free end of the backing covered panel is clampedinto the lower jaw of a tensile testing machine (described below) andthe free end of the tape into the upperjaw. The jaws are separated atthe rate of 7 12 inch (30.5 cm) per minute in order to peel the testtape off the release coated test backing. The results are: The averageadhesion value for the samples aged under condition (1) is 21 oz./inch(234g/cm) width, and for samples aged under condition (11) the adhesionvalue is 27 oz./inch (301 g/cm) width.

The tensile or adhesion testor consists of an upper jaw and a lowerjawsituated opposing each other in the same verticle plane. The upper jawis connected to a dial spring scale, Chatillon type 4200, capacity 15pounds (6.81 kilograms) set off in one half ounce (14.19 grams)increments, which is in turn rigidly attached to an upper frame member.The lower jaw is rigidly attached to a movable frame member such thatwhen the device is activated through a constant speed motor, gear trainand screw assembly, the lower jaw moves vertically downward at aconstant speed of 12 inches/minutes (30.5 centimeters/min). The upperjaw remains at rest.

Test C The test tapes pulled off in Test B are subjected to the adhesionto steel test described in PSTC-l. The adhesive tape pulled from therelease coated backing in Test B is applied directly to a clean steelpanel and rolled thereon once in each direction with a 4% pound (2.04Kg) roller at 12 in./min. (30.5 cm/min). The free end of the tape isdoubled back at an angle of 180 and peeled off the panel for a distanceof 1 inch (2.45 cm). The panel end from which the tape is removed isclamped into the lower jaw of the tensile testing machine described inTest 8 and the free end of the tape into the upper jaw. The jaws areseparated at a rate of 12 inch (305cm) per minute in order to peel thetape from the steel panel. The adhesion value for the tape agedaccording to Condition (1) is 29.5 oz./inch (323 g/cm) width, and forthe tape aged under Condition (11) the adhesion value is 25 oz./inch.(279 g/cm) width, indicating a loss of adhesiveness due to aging underCondition (11) of only about 15 percent, a loss well below the 40percent which is commercially acceptable.

Test D Other aged samples are further tested in accord with PSTC-6 inthe Rolling Ball Tack test: The adhesive tape 8 is stripped off by handat moderate speed (15-20 inches (38-57 cm)/second). and placed with theadhesive side up in line with the race way of the incline of the rollingball testing apparatus. A steel ball (7/16 inch( 1.1 1cm) diameter) isrolled down the incline. The average stopping distance of 6 tests foreach of the two aged condition is determined. The results are as follows: the stopping distance for the samples aged under condition (1) is1.5in. (3.8 cm), and for those aged under condition (11) is 0.9 in. (2.3cm) on the average.

Test E The release coated test backing is further tested forprintability by cutting the release coated test backing into stripsabout 4in. (10.2 cm) wide. The test backing,

165 line doctor roller, strips of ink are rolled down on the releaseside of the backing. The ink is allowed to air dry for more than 20minutes and then the adhesive tape previously identified is applied tothe inked sur face. To secure the tape to the surface, a 4% lb. (2.04

Kg) roller is rolled against the test tape 3 times in each direction.The laminate is aged for more than 20 minutes and then the adhesive tapeis pulled rapidly from the inked surface at an angle of 180 to the testbacking. The ink pick-off is 2 percent. This is the percent of inkcoverage that transferred to the test tape from the test backing. Theperformance factor as defined below, is determined to have a value of8.0.

EXAMPLES 2 20 Additional oligomers prepared essentially in the controllisted in Table 11 is ENDURA tape backing 13723 which is release coatedand is obtainable as a commercial tape backing product from W. R. Grace& Co. It is used in the same manner as the tape backing of the presentinvention.

TABLE 1 Preparation of R-S-(Acry1onitri1e),,-(Acrylic Acid),,'H

Acrylonitrile Acrylic Mercaptan Catalyst Conversion Examples R a+ba/(a+b) g Acid g g g/mole Conversion monomer 2 primary tridecyl 12.10.256 16.0 63.0 21.0 0.85

3 n-tetradecyl 12.9 0.256 16.0 63.0 21.0 0.85 59 4 n hexadecyl 14.40.256 16.0 63.0 21.0 0.85 74 5 t-hexadecyl 14.4 0.256 16.0 63.0 21.00.85 80 6 n-octadecyl 8.0 0.125 .6.4 59.8 34.0 1.01 64 7 nbctadecyl 8.00.250 12.8 52.5 34.8 1.04 52 8 8.1 0.370 20.0 45.1 35.5 1.07 53 9 15.90.000 0.0 79.8 20.0 0.90 99 10 16.0 0.375 24.0 54.6 21.7 0.83 75 11 16.10.496 32.8 45.1 22.2 0.82 62 12 0 24.2 0.124 8.0 77.7 14.5 0.81 13 24.10.249 16.8 68.2 15.0 0.80 77 14 24.0 0.371 25.6 511.8 15.5 0.76 88 15 322 0.000 0.0 89.2 11.0 0.81 16 32.0 0.250 17.6 71.4 11.8 0.80 87 17 31.90.498 36.8 50.4 12.5 0.72 86 18 40.6 0.128 8.8 81.) 9.2 0.77 94 19 40.10.376 28.0 63.0 10.0 0.71 84 TABLE l-continued Preparation ofR-S-(Acrylonitrileh-(Acrylic Acid ),-H m Acrylonitrile Acrylic MercaptanCatalyst Conversion Examples R a+b a/(a+b) g Acid g g g/mole Conversionmonomer 20 48.8 0.254 18.4 73.5 8.0 0.80 87 Conditions: 'Bathtemperature pre set to 50C 127 ml isopropanol tor-.11 Reaction time 16hours. no DMA added TABLE 11 Test: A B C D E Results in: Rating oz/in.width in. of roll 7 -pick-off Condition: 1 ll 1 ll 1 l1 1 11 Example PF"2 l 3 27 35.5 29.5 28.5 0.5 0.35 l 5.4 3 l 3 26 34.5 29.5 20 1.15 1.0 41.0 4 I 2.5 21 36 33 23 1.15 1.0 2 2.6 5 2 5* 28 41 29 30 0.75 0.15 20.3 6 2 1 23.5 29 27 17 0.5 0.5 7.5 1.8 7 1.3 1.1 24 29 31 15 0.8 3.25 51.5 8 1.1 l 23 27.5 34 16.5 1.4 2.6 1.2 9 l 2 21.5 31 34 21.5 1.15 0.620 0.5 10 l 2 24 36 32 24 1.0 0.9 l 5.6 11 1.3 3 23 34 30 23.5 1.0 0.55l 4.0 12 l l 24 30 32 24.5 1.35 0.65 12.5 1.6 13 l 2.5 24 37 33 30 1.150.4 3 2.9 14 2 2 23 31 30 26 1.25 0.65 3 3.7 15 l 3 23.5 28 32.5 24 1.350.75 5 1.3 16 2 1 24.5 32 31.5 24 1.0 1.5 3 4.2 17 3 3 23 33.5 33 271.25 0.5 2 2.9 18 l l 22 31.5 29 22 1.25 0.6 4 3.8 19 2 2 24.5 32.5 3023.5 1.0 0.65 3 3.2 20 2 1 22 31.5 27 1.0 1.0 4 4.3 Control 1 5* 20.835.5 29.5 27 1.0 1.15 1 0.3

Remarks:

delamination Performance Factor As already mentioned previously therelease agents of this invention combine desirable properties in aunique way which other materials, including those widly used by theindustry do not achieve, i.e., as the various test results indicate. notonly do these compoundspermit good to excellent adhesion as demonstratedby Test C and D. but also remarkable printability according to the TestE results. Their superior performance is further emphasized by the lowor at least acceptable adhesion to the backing (see Test 8) but peciallyby the extraordinary ease with which rapid paration of the adhesivecoated tape from the release coated backing can be accomplished evenafter having been exposed to the severe Aging Condition (11). Theseoverall properties of the release agents of this invention aresummarized by the Performance Factor (PF) as expressed by the followingequation:

wherein, for any given example further underline the qualities of theinstant release agents ranging from at least equal to vastly superiorover those of the Control which is a widely accepted commercial product.Although a PF- value of as low as 0.3 may be commercially acceptableunder certain conditions, compounds having a PF-value of 2.00 or higherare preferred, and compounds having a PF- value of 3.0 or more areparticularly desirable. Although the Performance Factor values areapplicable only to the systems used herein it is believed that employingdifferent testing materials will not appreciably change the values inrelation to each other.

EXAMPLE 21 The preparation of the oligomers may be readily accomplishedon a larger scale; therefore, the following materials are added to a oneliter resin flask following the general procedure outlined above inorder to produce the oligomer:

n-octadecyl S (acrylonitrileh- (acrylic acidhz H The bath temperature ispreset to 39C.

60 ml acrylonitrile (48 g, 0.906 moles) ml acrylic acid (189 g, 2.63moles) 63 g n-octadecyl mercaptan; 97% (0.220 moles) 300 ml isopropanol3 g decanoyl peroxide 1 ml DMA In accordance with the general formula: Rnoctadecyl; a b 16.0; a/(a+b) 0.256; acrylcnitrile g 16; acrylic acid g63; mercaptan g 21; catalyst, g/mole mono .85; DMA is added in order toincrease the reaction rate.

After one-half hour the temperature rises to about 46C over a period of1 hour, and returns to about 40C 11 after an additional 1% hours. Tenmore drops of DMA are added and a slight exotherm is observed. Afterthree more hours, the reaction flask is removed from the bath. The totalreaction time is 6 hours. The conversion is 99%, and the solids are55.6%. The acidic reaction product is a clear, straw colored solution at40C, but becomes a viscous, two phase slurry upon cooling to roomtemperature.

Neutralization is carried out as follows: 300 ml of water are added tothe acidic reaction product. Neutralization is preformed using oneequivlant of KOH (about 327 g of 45% aqueous KOH). After 23% of the KOHhas been added the mixture is stripped of the unreacted monomer and thealcohol by placing the mixture in a Buechi Rotovapor (Model VE-SO) undervacuum. After stripping, the remaining 77% of the KOH is added until asolution pH of 9 is obtained. When tested as a release agent asdescribed in Example l the thus prepared oligomer exhibits essentiallythe same results as the comparable Example 1 oligomer.

No present day release coating system for pressure sensitive tape offersthe unique combination of efficient or controlled release, freedom fromadhesive degradation, printability by commonly used low costflexographic inks, stability of these properties under severe agingconditions along with non toxic and pollution free applicationconditions that is offered by the instant invention. While nearly all ofthe above advantages can be found separately or in partial combinationthe need for a single system which provides all of the above has beenobvious among practitioners of the art for many years.

It is claimed;

1. A pressure sensitive adhesive tape comprising a flexible backingwhich has a pressure sensitive adhesive on one side and a releasecoating on the other side, said release coating consisting essentiallyof an oligomer represented by the formula wherein R is a linear orbranched alkyl radical having 12 to 22 carbon atoms; R and R may be thesame or different and are hydrogen, a -CH or C H group; R is hydrogen, aCH;,. -C H or COOR" group; R is hydrogen, a CH;,, -C H -COOR" or -CH-COOR" group provided R is other than -COOR if R is -COOR"' or -CH COOR Ris hydrogen or a cation based on an alkali metal, ammonia or an amine;(a+b) is from 4 to 100; a/(a+b) is from 0.0 to 0.6; and n has a value of0,l or 2.

2. The adhesive tape of claim 1, wherein said R" is selected from thegroup consisting of hydrogen, lithium, sodium and potassium.

3. The adhesive tape of claim 2, wherein R is a linear or branchedprimary alkyl or a linear secondary alkyl group having from 13 tocarbons; R, R R, and R are hydrogen; (a+b) is from 8 to 50, a/(a i-b) isfrom 0.0 to 0.5, and n is 0.

4. The adhesive tape of claim 3, wherein R is a linear or branchedprimary alkyl radical having 13 to 18 carbon atoms.

5. The adhesive tape of claim 4, wherein R is potassium.

6. The adhesive tape of claim 3, wherein (a+b) is from 12 to 50 anda/(a+b) is from 0.25 to 0.5.

7. The adhesive tape of claim 1, wherein said tape is wound upon itself.

8. The adhesive tape of claim 1, wherein said backing is a crepedcellulose sheet saturated with ABS latex, and is coated with a vinyllatex base coat between the backing and said release coating.

9. The adhesive tape of claim l, wherein said oligomer is present in aquantity of 0.00l to 0.1 ounces per square yard.

10. A flexible backing for pressure sensitive adhesive tape having on atleast one side a release coating consisting essentially of an oligomerhaving a structural formula wherein R is a linear or branched alkylradical having 12 to 22 carbon atoms; R and R may be the same ordifferent and are hydrogen, a -CH,, or -C H group; R is hydrogen, a -CHC H or COOR groups; R is hydrogen, a -CH;,, C H -COOR or CH- COOR group,provided R is other than -COOR" if R is COOR" or CH COOR R is hydrogenor a cation based on an alkali metal, ammonia or an amine; (a+b) is from4 to I00; a/(a+b) is from 0.0 to 0.6; and n has a value of 0, l or 2.

11. The flexible backing of claim 10, wherein said R is selected fromthe group consisting of hydrogen, lithium, sodium and potassium.

12. The flexible backing of claim 11 wherein R is a linear or branchedprimary alkyl or a linear secondary alkyl group having from 13 to 20carbons; R, R R and R are hydrogen; (a+b) is from 8 to 50, a/(a-l b) isfrom 0.0 to 0.5, and n is 0.

13. The flexible backing of claims 12, wherein R is a linear or branchedprimary alkyl radical having 13 to 18 carbon atoms.

14. The flexible backing of claim [3, wherein R is potassium.

15. The flexible backing of claim 12, wherein (a+b) is from l2 to 50 anda/(a+b) is from 0.25 to 0.5.

16. The flexible backing of claim 10, wherein said backing is a crepedcellulose sheet saturated with a latex chosen from the group consistingof ABS, acrylic, SBR, acrylonitrile, neoprene and copolymers and blendsthereof, and is coated with a latex base coat between the backing andsaid release coating, said latex base coat being chosen from the groupconsisting of vinyl and acrylic latices and mixtures thereof.

17. The flexible backing of claim 10, wherein said oligomer is presentin a quantity of 0.001 to 0.] ounces per square yard.

18. An improved laminar structure having a flexible tape coated with apressure sensitive adhesive on one side, a release coating adjacent tothe adhesive and a flexible backing adhering to the release coating, theimprovement comprising said release coating consisting essentially of arelease agent which is an oligomer having the structural formula whereinR is a linear or branched alkyl radical having 12 to 22 carbon atoms; Rand R may be the same or different and are hydrogen, a CH or -C H group;R" is hydrogen, a CH -C H or COOR group; R is hydrogen, a CH C H COOR orCH- COOR group, provided R is other than COOR if R is COOR or CH COOR'';R is hydrogen or a cation based on an alkali metal, ammonia or an amine;(a+b) is from 4 to I00, a/(a+b) is from 0.0 to 0.6 and n has a value of0, l or 2.

19. The laminar structure of claim 18, wherein R is a linear or branchedprimary alkyl or a linear secondary alkyl group having from l3 tocarbons; R, R, R and R are hydrogen; (a+b) is from 8 to 50, a/(a-i-b) isfrom 0.0 to 0.5, and n is 0.

20. The laminar structure of claim [9 wherein R is a linear or branchedprimary alkyl radical having 13 to [8 carbon atoms, R is potassium and(a+b) is from 12 to 50 and a/(a-l-b) is from 0.25 to 0.5.

21. The laminar structure of claim 18 wherein said oligomer is presentin a quantity of 0.001 to 0.1 ounces per square yard.

22. A structure comprising a substrate, a release coat on said substrateand a pressure sensitive adhesive on said release coat, said releasecoat consisting essentially of an oligomer represented by the formulawherein R is a linear or branched alkyl radical having 12 to 22 carbonatoms; R' and R may be the same or different and are hydrogen, a -CH or---C H: group; R is hydrogen, a CH C H or --COOR" group; R is hydrogen,a -CH -C H COOR or CH- COOR" group, provided R is other than --COOR if Ris COOR or CH COOR"; R is hydrogen or a cation based on an alkali metal,ammonia or an amine: (a+b) is from 4 to I00; a/(a-l-b) is from 0.0 to0.6; and n has a value of 0, l or 2.

23. The structure of claim 22 wh rein R is a linear or branched primaryalkyl or a linear secondary alkyl group having from l3 to 20 carbons; R,R R and R are hydrogen; (a+b) is from 8 to 50, a/(a-l-b) is from 0.0 to0.5, and n is 0.

24. The structure of claim 23 wherein R is a linear or branched primaryalkyl radical having l3 to l8 carbon atoms, R is potassium and (a+b) isfrom 12 to 50 and a/(a-i-b) is from 0.25 to 0.5.

25. The structure of claim 22 wherein said oligomer is present in aquantity of 0.00l to 0.] ounces per square yard.

26. A strucutre comprising an adhesive engaged with a release coating,said release coating consisting essentially of an oligomer representedby the formula wherein R is a linear or branched alkyl radical having l2to 22 carbon atoms; R and R may be the same of different and arehydrogen, a CH or C H,, group; R" is hydrogen, a CH;,, C H or COORgroup; R is hydrogen, a -CH;,, C H -COOR" or CH- COOR group, provided Ris other than COOR if R is COOR" or CH COOR R is hydrogen or a cationbased on an alkali metal, ammonia or an amine; (a+b) is from 4 to I00;a/(a-l-b) is from 0.0 to 0.6; and n has a value of 0,! or 2.

27. The structure ofclaim 26 wherein R is a linear or branched primaryalkyl or a linear secondary alkyl group having from 13 to 20 carbons; R,R, R and R are hydrogen; (a+b) is from 8 to 50, a/(a+b) is from 0.0 to0.5, and n is 0.

28. The structure of claim 27, wherein R is a linear or branched primaryalkyl radical having l3 to 18 carbon atoms; R" is potassium, (a+b) isfrom l2 to 50; and al(a+b) is from 0.25 to 0.5.

29. The structure of claim 26 wherein said oligomer is present in aquantity of 0.001 to 0.l ounces per square yard.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent 3 ,928 ,690Dated December 23 1975 Robert A. Settineri et a1. Inventor(s) It iscertified that error appears in the aboveidentified patent and that saidLetters Patent are hereby corrected as shown below:

On the cover sheet assignee should read W. R. Grace and Co., Cambridge,Mass., and

Uniroyal Inc., Middlebury, Conn.

Column 12, line 29, groups" should read 2' group Column 14, line 28,"of" should read or Signed and Scaled this A Ilesl:

RUTH C. MASON C. MARSHALL DANN Arlesn'ng Officer Commissioner 0] Palenrsand Trademarks

1. A PRESSURE SENSITIVE ADHESIVE TAPE COMPRISING A FLEXIBLE BACKINGWHICH HAS A PRESSURE SENSITIVE ADHESIVE ON ONE SIDE AND A RELASE COATINGON THE OTHER SIDE, SAID RELEASE COATING CONSISTING ESSENTIALLY OF ANOLIGOMER REPRESENTED BY THE FORMULA
 2. The adhesive tape of claim 1,wherein said R5 is selected from the group consisting of hydrogen,lithium, sodium and potassium.
 3. The adhesive tape of claim 2, whereinR is a linear or branched primary alkyl or a linear secondary alkylgroup having from 13 to 20 carbons; R1, R2, R3, and R4 are hydrogen;(a+b) is from 8 to 50, a/(a+b) is from 0.0 to 0.5, and n is
 0. 4. Theadhesive tape of claim 3, wherein R is a linear or branched primaryalkyl radical having 13 to 18 carbon atoms.
 5. The adhesive tape ofclaim 4, wherein R5 is potassium.
 6. The adhesive tape of claim 3,wherein (a+b) is from 12 to 50 and a/(a+b) is from 0.25 to 0.5.
 7. Theadhesive tape of claim 1, wherein said tape is wound upon itself.
 8. Theadhesive tape of claim 1, wherein said backing is a creped cellulosesheet saturated with ABS latex, and is coated with a vinyl latex basecoat between the backing and said release coating.
 9. The adhesive tapeof claim 1, wherein said oligomer is present in a quantity of 0.001 to0.1 ounces per square yard.
 10. A FLEXIBLE BACKING FOR PRESSURESENSITIVE ADHESIVE TAPE HAVING ON AT LEAST ONE SIDE A RELEASE COATINGCONSISTING ESSENTIALLY OF AN OLIGOMER HAVING A STRUCTURAL FORMULA 11.The flexible backing of claim 10, wherein said R5 is selected from thegroup consisting of hydrogen, lithium, sodium and potassium.
 12. Theflexible backing of claim 11 wherein R is a linear or branched primaryalkyl or a linear secondary alkyl group having from 13 to 20 carbons;R1, R2, R3 and R4 are hydrogen; (a+b) is from 8 to 50, a/(a+b) is from0.0 to 0.5, and n is
 0. 13. The flexible backing of claims 12, wherein Ris a linear or branched primary alkyl radical having 13 to 18 carbonatoms.
 14. The flexible backing of claim 13, wherein R5 is potassium.15. The flexible backing of claim 12, wherein (a+b) is from 12 to 50 anda/(a+b) is from 0.25 to 0.5.
 16. The flexible backing of claim 10,wherein said backing is a creped cellulose sheet saturated with a latexchosen from the group consisting of ABS, acrylic, SBR, acrylonitrile,neoprene and copolymers and blends thereof, and is coated with a latexbase coat between the backing and said release coating, said latex basecoat being chosen from the group consisting of vinyl and acrylic laticesand mixtures thereof.
 17. The flexible backing of claim 10, wherein saidoligomer is present in a quantity of 0.001 to 0.1 ounces per squareyard.
 18. An improved laminar structure having a flexible tape coatedwith a pressure sensitive adhesive on one side, a release coatingadjacent to the adhesive and a flexible backing adhering to the releasecoating, the improvement comprising said release coating consistingessentially of a release agent which is an oligomer having thestructural formula
 19. The laminar structure of claim 18, wherein R is alinear or branched primary alkyl or a linear secondary alkyl grouphaving from 13 to 20 carbons; R1, R2, R3 and R4 are hydrogen; (a+b) isfrom 8 to 50, a/(a+b) is from 0.0 to 0.5, and n is
 0. 20. The laminarstructure of claim 19 wherein R is a linear or branched primary alkylradical having 13 to 18 carbon atoms, R5 is potassium and (a+b) is from12 to 50 and a/(a+b) is from 0.25 to 0.5.
 21. The laminar structure ofclaim 18 wherein said oligomer is present in a quantity of 0.001 to 0.1ounces per square yard.
 22. A structure comprising a substrate, arelease coat on said substrate and a pressure sensitive adhesive on saidrelease coat, said release coat consisting essentially of an oligomerrepresented by the formula
 23. The structure of claim 22 wherein R is alinear or branched primary alkyl or a linear secondary alkyl grouphaving from 13 to 20 carbons; R1, R2, R3 and R4 are hydrogen; (a+b) isfrom 8 to 50, a/(a+b) is from 0.0 to 0.5, and n is
 0. 24. The structureof claim 23 wherein R is a linear or branched primary alkyl radicalhaving 13 to 18 carbon atoms, R5 is potassium and (a+b) is from 12 to 50and a/(a+b) is from 0.25 to 0.5.
 25. The structure of claim 22 whereinsaid oligomer is present in a quantity of 0.001 to 0.1 ounces per squareyard.
 26. A STRUCTURE COMPRISING AN ADHESIVE ENGAGED WITH A RELEASECOATING, SAID REPRESENTED BY THE FORMULA
 27. The structure of claim 26wherein R is a linear or branched primary alkyl or a linear secondaryalkyl group having from 13 to 20 carbons; R1, R2, R3 and R4 arehydrogen; (a+b) is from 8 to 50, a/(a+b) is from 0.0 to 0.5, and n is 0.28. The structure of claim 27, wherein R is a linear or branched primaryalkyl radical having 13 to 18 carbon atoms; R5 is potassium, (a+b) isfrom 12 to 50; and a/(a+b) is from 0.25 to 0.5.
 29. The structure ofclaim 26 wherein said oligomer is present in a quantity of 0.001 to 0.1ounces per square yard.